base class, extends NXobject


A neutron velocity selector


No symbol table

Groups cited:

NXgeometry, NXoff_geometry, NXtransformations


@default: (optional) NX_CHAR

Declares which child group contains a path leading to a NXdata group.

It is recommended (as of NIAC2014) to use this attribute to help define the path to the default dataset to be plotted. See https://www.nexusformat.org/2014_How_to_find_default_data.html for a summary of the discussion.

type: (optional) NX_CHAR

velocity selector type

rotation_speed: (optional) NX_FLOAT {units=NX_FREQUENCY}

velocity selector rotation speed

radius: (optional) NX_FLOAT {units=NX_LENGTH}

radius at beam centre

spwidth: (optional) NX_FLOAT {units=NX_LENGTH}

spoke width at beam centre

length: (optional) NX_FLOAT {units=NX_LENGTH}

rotor length

num: (optional) NX_INT {units=NX_UNITLESS}

number of spokes/lamella

twist: (optional) NX_FLOAT {units=NX_ANGLE}

twist angle along axis

table: (optional) NX_FLOAT {units=NX_ANGLE}

offset vertical angle

height: (optional) NX_FLOAT {units=NX_LENGTH}

input beam height

width: (optional) NX_FLOAT {units=NX_LENGTH}

input beam width

wavelength: (optional) NX_FLOAT {units=NX_WAVELENGTH}


wavelength_spread: (optional) NX_FLOAT {units=NX_WAVELENGTH}

deviation FWHM /Wavelength

depends_on: (optional) NX_CHAR

NeXus positions components by applying a set of translations and rotations to apply to the component starting from 0, 0, 0. The order of these operations is critical and forms what NeXus calls a dependency chain. The depends_on field defines the path to the top most operation of the dependency chain or the string “.” if located in the origin. Usually these operations are stored in a NXtransformations group. But NeXus allows them to be stored anywhere.

geometry: (optional) NXgeometry

DEPRECATED: Use the field depends_on and NXtransformations to position the velocity selector and NXoff_geometry to describe its shape instead

OFF_GEOMETRY: (optional) NXoff_geometry

This group describes the shape of the beam line component

TRANSFORMATIONS: (optional) NXtransformations

This is the group recommended for holding the chain of translation and rotation operations necessary to position the component within the instrument. The dependency chain may however traverse similar groups in other component groups.

Hypertext Anchors

List of hypertext anchors for all groups, fields, attributes, and links defined in this class.

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